Why can I only see the prototype of the constructor function?-CodePudding

function Dog(name) {
  this.name = name;
}
Dog.prototype = {
  constructor: Dog,
  age: 16,
  eat: function() {
    console.log('this function works')
  }
}

let beagle = new Dog("Snoopy");

console.log(Dog.prototype);
console.log(beagle.prototype);
beagle.eat();

The console outputs the prototype for the constructor function, but returns undefined for the prototype of the beagle. If I call eat() on the beagle however, it outputs 'This function works'. Why is the prototype undefined, despite the fact that I can still call the function eat() on the beagle object?

CodePudding user response：

Prototype is the property of the constructor function, so that's why beagle don't have beagle.prototype as a property but all ordinary objects in JavaScript have an internal prototype slot which is not a .prototype property but __proto__ and you can access it with .__proto__ like this:

function Dog(name) {
  this.name = name;
}
Dog.prototype = {
  constructor: Dog,
  age: 16,
  eat: function() {
    console.log('this function works')
  }
}

let beagle = new Dog("Snoopy");

console.log(Dog.prototype);
console.log(beagle.__proto__);
beagle.eat();